The invention relates to a method for the treatment of wastes containing silicone emulsions for separating silicone oil and water from the wastes. In particular, the invention relates to a method for separating the emulsion by the addition of chemicals, such as, but not limited to, sodium hydroxide, sodium carbonate, and sodium chloride, or combinations of these chemicals, to produce two separate phases containing silicone oil and water.
FIG. 1 schematically illustrates a prior system for silicone treatment. In FIG. 1, silicone emulsions are produced in a batch method, such as, but not limited to, making a surfactant blend containing different types and concentrations of emulsifiers and biocides. The surfactant blend is mixed with silicone oil to form a surfactant paste. Next, the surfactant paste is diluted with water to form emulsion products. A majority of the waste is generated when mixing vessels and lines are cleaned for transition to a different silicone emulsion grade product.
A current practice for cleaning the tanks and lines includes washing mixing tanks and lines in cleaning stages. In the first cleaning stage, the tanks are filled to approximately ⅓ of their capacity, and the wash water is recirculated throughout the tanks and lines. This wash water, which contains the majority of the emulsions, is mixed with other wastes, and can be burned in an incinerator. The cost of running an incinerator, which burns mostly water, is high, and often the wash water load to the incinerator exceeds its capacity. However, subsequent washes contain very little emulsions, and can be sent directly to a wastewater treatment plant (WWTP).
Presently, chemicals are available that can be used to break or separate emulsions. The choices of chemicals depend on the specific compositions of the emulsions containing wastes. There are several commercially available emulsion separators. In testing, some cationic surfactants, such as Atlas-G265 and G250, manufactured by ICI Surfactants®, failed to adequately separate the emulsion. Likewise, Triton X-50 manufactured by Union Carbide® and sodium dodecylbenzene sulfonic acid could not adequately separate the silicone emulsions.
Other general types of emulsion separators that were tested for their ability to separate the silicone emulsion include quaternary polyamide, polyamide polymer, aluminum salts, ferric sulfate, polyquaternary ammonium chloride, polyamine, and a sodium aluminate solution which contains 20-40% sodium aluminate and 5-10% sodium hydroxide. All of these, except sodium aluminate, failed to adequately separate the silicone emulsion. However, to separate the emulsion, 13% volume basis of sodium aluminate solution must be added. This value may be too high and may result in a costly method.
Therefore, a need exists to develop effective methods for separating silicone oil and water from emulsion wastes and to reduce the cost associated with the disposal of such wastes.